The invention relates to a marine fuel system for a fuel injected engine, and more particularly to the fuel vapor supply from a vapor separator. The invention arose during development efforts directed to solving hot restart problems in fuel injected marine internal combustion engines.
In fuel injected engines, it is important to accurately control the quantity of fuel delivered to the engine through the fuel injectors. Many systems have been designed to control the operation of a fuel injector to accurately meter the fuel to the engine. It is common to use a high pressure pump to supply fuel to the injectors with a pressure regulator providing an essentially constant fuel pressure at the injector. Excess fuel, i.e. the amount over and above that required by the engine, is recirculated back to the fuel tank. In marine applications where the fuel tank is located at significant distances from the engine, it is undesirable to provide an extended fuel return line to the fuel tank, since fire or other hazards could arise.
Some prior systems have used recirculating type fuel injection pumps with the excess fuel returning immediately to the inlet of the pump. In such systems, however, if the engine is operated at idle or low speeds for significant periods of time, the recirculating fuel accumulates heat from the pump and may vaporize. This typically would reduce the output of the pump to such a degree that adequate fuel pressure could no longer be maintained at the fuel injector.
It is known in the prior art to solve the above noted fuel vaporization problem by providing a fuel vapor separator. A first fuel pump draws fuel from the fuel tank, a second fuel pump receives fuel from the first pump and provides fuel under pressure to the fuel injector. A vapor separator is connected between the first and second pumps to remove fuel vapors from the fuel supplied to the second pump.
It has been found that even with a vapor separator, hot restart problems may still occur. It has also been found that upon rapid or snap engine deceleration, the engine may idle rough or stall. The present invention addresses and solves these problems.
It has been found that fuel foaming in the vapor separator spills into the inlet manifold of the induction system under high vacuum conditions. It has also been found that after turn-off of the engine, engine heat causes saturated fuel vapor to accumulate in the vapor separator which flows to the inlet manifold.
In the present invention, a fitting is provided in the vapor supply line and limits fuel vapor supplied from the vapor separator to the induction system at peak vacuum from the induction system during rapid engine deceleration. This prevents an overly rich fuel-air mixture in the induction system otherwise causing rough idling or stalling.
The fitting includes a vacuum bleed orifice passage partially venting vacuum from the induction system to atmosphere, to limit the peak vacuum applied to the vapor separator. The lower vacuum reduces boiling and vapor bubbles in the vapor separator. The fitting also includes a flow restrictor passage limiting the volume of flow of fuel vapor from the vapor separator to the induction system. The elimination of the overly rich mixture from the vapor separator to the induction system also solves the above noted hot restart problem.